From 4198ce4de86d2144ce127bba0d263a005926acf2 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <darrick.wong@oracle.com>
Date: Sat, 24 Oct 2015 00:30:02 -0400
Subject: [PATCH 03/16] libext2fs: automatically enable meta_bg to avoid
filling up BG 0
commit 03940aac5492879ef365b07e69105a98f4dbabf9
If during formatting we'd lose more than 75% a block group to group
descriptors and other metadata, enable the meta_bg feature. This
enables us to create >500T filesystems with default options.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
lib/ext2fs/initialize.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c
index 3548c56c..0b8355d8 100644
--- a/lib/ext2fs/initialize.c
+++ b/lib/ext2fs/initialize.c
@@ -379,6 +379,11 @@ ipg_retry:
overhead = (int) (3 + fs->inode_blocks_per_group +
super->s_reserved_gdt_blocks);
+ /* Enable meta_bg if we'd lose more than 3/4 of a BG to GDT blocks. */
+ if (super->s_reserved_gdt_blocks + fs->desc_blocks >
+ super->s_blocks_per_group * 3 / 4)
+ fs->super->s_feature_incompat |= EXT2_FEATURE_INCOMPAT_META_BG;
+
if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
overhead++;
else
--
2.20.1